(1) Field of the Invention
This invention relates to the dehydration and demineralization of diluted bitumen emulsions obtained from tar sands and the like. More particularly, this invention relates to the treatment of such diluted bitumen by electric field treatment to resolve the emulsions, whereby aqueous material carrying undissolved particulate mineral solids separate out. As used herein, the term "emulsion" is used to include dispersions resembling emulsions as well as true emulsions.
(2) Description of the Prior Art
One of the processes employed in the production of hydrocarbons from tar sands is the hot water process of bitumen recovery. In this process, the bitumen is produced as a froth on top of the water. A diluent capable of dissolving the bitumen, usually a hydrocarbon liquid such as benzene, xylene, toluene, naphtha, kerosene, furnace distillates, Diesel fuels, or the like, is added to the bitumen to facilitate water and solids separation. Such separation is then accomplished by centrifugation, utilizing, for example, low speed "Bird" scroll-type centrifuges followed by high speed "Westfalia" centrifuges (available commercially from the Bird Machine Company and Westfalia Separator A. G., respectively).
Among the patents describing processes of the above or similar type are Canadian Pat. No. 918,091 to Evans and Camp and U.S. Pat. No. 2,968,603 to Gordon R. Coulson, No. 3,900,389 to Robert A. Baillie, and No. 4,035,282 to Frederick C. Stuchberry and Alfred E. Backstrom. Most important of the tar sands to which such processes are applied are the Athabasca tar sands found primarily in Northern Alberta, Canada.
The centrifuged, diluted, bitumen still contains a considerable quantity of water and particulate mineral solids. It is typical to find about 25-30 wt. % water and about 5 to 10 wt. % mineral solids in the diluted bitumen feed to the Bird centrifuge; and about 20 to 25 wt. % water and about 2 to 5 wt. % mineral solids in the diluted bitumen feed to the Westfalia centrifuge (produced by the Bird Centrifuge). The product from the Westfalia Centrifuge typically contains about 5 to 10 wt. % water and about 1 to 3 wt. % mineral solids.
Efforts to upgrade the quality of the diluted bitumen have been beset with difficulties and considerable research has gone into achieving an efficient process for producing really clean diluted bitumen with minimum loss of hydrocarbons.